This invention concerns novel aminoalkylated polyacrylamide gels particularly useful for the recovery of oil from subterranean reservoirs.
The strata of subterranean oil-producing reservoirs are rarely formed of homogeneous masses, but rather are usually layered, with significant variation in permeability from zone to zone. This permeability variation is often further complicated by fractures, both natural and man-made, in the strata. Such heterogeneity at the injector well leads to rapid breakthrough of the water or other flooding media, such as carbon dioxide or hydrocarbon-miscible agents, being used in an enhanced oil recovery operation. This results in poor sweep efficiency and underproduction of recoverable reserves. At the producer well, the heterogeneity causes excessive encroachment of the flooding media with attendant higher production costs. Water encroachment at the well can also arise from coning of bottom water.
Many methods for modifying the fluid flow characteristics in the near wellbore area of affected wells to improve oil production have been tried. In recent years, the use of cross-linked polymer gels has become the method of choice since these gels can reduce zone permeability without complete plugging and, with producer well treatments, allow continued oil production. Such gels include ionically cross-linked polyacrylamide chrome gels and, more recently, dialdehyde cross-linked polyacrylamide gels, as exemplified by the gel of U.S. Pat. No. 4,155,405.
While such gels have proven to be beneficial in improving oil production efficiency, the need for a gel of improved permeability and strength characteristics still exists. It is therefore the primary objective of the present invention to satisfy this need.